The present invention is directed to a method of electroplating walls of nonmetallic dielectric holes in a substrate while selectively plating a pattern on the surface which lies outside of the holes. The present invention allows simultaneous pattern plating of a conductive surface layer whereby only portions of the conductive layer are plated while at the same time plating holes extending through the conductive layer and an insulating layer.
It is known in the prior art to electroplate a dielectric base employing a catalyst. Radowsky et al. U.S. Pat. No. 3,099,608 discloses a method of obtaining a conductive coating on through holes in printed circuit boards by depositing a thin nonconductive film of palladium metal and electroplating directly over the nonconductive palladium film. British Pat. No. 2,123,036 discloses a method for metallizing nonmetallic surfaces by electroplating in a vessel provided with a counter electrode and provided with an electroplating bath solution containing a metal (B) to be electroplated with the nonmetallic surfaces being provided with metallic sites of another metal (A) to obtain preferential deposition of metal (B) on metal (A).
German Preliminary Published Application No. DE 3304 004 discloses a process for the production of through hole plated circuits in perforations of a printed circuit board by first activating the surfaces of the perforations by means of a catalyst and then metallizing by galvanic metal deposition.
In spite of the disclosures of the above publication a need is present for a process which allows direct electroplating of nonconductive through holes extending through an insulating layer and portions of at least one conductive layer.